linux-kernel - Re: [v2 3/4] platform: (TS-5500) add LED support

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Message-ID: <20110830211528.GU2061@opensource.wolfsonmicro.com>
Date:	Tue, 30 Aug 2011 22:15:29 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Jonas Fonseca <jonas.fonseca@...oirfairelinux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [v2 3/4] platform: (TS-5500) add LED support

On Tue, Aug 30, 2011 at 05:14:24PM -0400, Vivien Didelot wrote:
> "H. Peter Anvin" <hpa@...or.com> wrote:
> > On 08/29/2011 03:16 PM, Mark Brown wrote:

> > > Can you not do outb() from atomic context?  The reason lots of LED
> > > drivers update the hardware in a workqueue is that they communicate
> > > with the hardware over buses that can't be used in atomic context
> > > like I2C or SPI but if that's not an issue then the workqueue is
> > > not required and the code can be simplified.

> > outb() can definitely be executed from atomic context.

> Good to know, thanks. I removed the work_struct and instead lock a mutex
> before setting led->new_brightness and calling outb().

You can't take a mutex in atomic context...
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